The present invention relates to a steam or vapor engine which uses a refrigerant as its working medium and which is provided with a number of bellows each forming an expansion chamber for receiving the working medium and changing its volume under the influence of the pressure exerted by the vaporized working medium. Engines of this type are provided with a crank shaft from which mechanical power can be taken off as well as with valves which serve to control the flow of the working medium to the interior of the bellows.
One type of working medium which is particularly suited for use in such engines is a refrigerant known commercially as a freon, which is a halogenated hydrocarbon and particularly halogenated methane or ethane. Such refrigerants are not inherently dangerous, they do not react chemically to any significant extent with the seals with which engines of this type are equipped, and they have relatively low temperatures of vaporization, so that it is practical to use such refrigerants as the working medium for the purpose of obtaining kinetic energy even if operating conditions are such that only relatively small temperature differences are available. A vapor-type engine according to the present invention can therefore be used in a system which incorporates two heat exchangers, one of which is a solar heat exchanger that serves to heat up water by means of solar energy and to vaporize the refrigerant, the second heat exchanger being one which is connected to the medium outlet of the engine and which, with the help of water which is itself at normal temperature, e.g., at an ambient or room temperature of between 20.degree. to 25.degree. C., condenses the refrigerant coming from the engine. If desired, a circulating pump can be inserted between the refrigerant output of the second heat exchanger and the refrigerant input of the first heat exchanger. The foregoing is, of course, but one exemplary application for a vapor engine of the type involved here.
While a vapor engine using a refrigerant as its working medium makes it possible to utilize small temperature differences, considerable care has to be taken in properly designing the engine. For one thing, the vapor pressure exerted by the refrigerant will usually be relatively small, so that the engine should operate with as little friction as possible. Consequently, it is not always readily possible to let the expansion chambers be constituted by conventional piston-and-cylinder arrangements. For this reason, as well as in view of the relatively small amount of input energy available for such vapor engines, one cannot do with conventional valves and valve actuating arrangements. Moreover, while it is true that refrigerants consisting of halogenated hydrocarbons will liberate lubricants that are useful to lubricate the various component parts of the engine and which will penetrate even into small spaces, the very fact that such fine lubricants are present bring various sealing problems with them. Moreover, suitable provision has to be made for draining the lubricating oils when the engine is shut down, and for lubricating oils which are carried along by condensation formed as the result of expansion in the wet vapor phase.
It is, therefore, the primary object of the present invention to provide a vapor engine of the above-described type which allows the use of modern refrigerants as its working medium, which is of uncomplicated structure, and which is able to fulfill the above-stated criteria.